A bipolar medical instrument is disclosed for cutting tissue under the action of high-frequency current, wherein the instrument extends along a longitudinal direction from a proximal end to a distal end, and wherein an active electrode and a neutral electrode, adjacent to the active electrode, are arranged at the distal end. There is also disclosed an electrosurgical system with a high-frequency generator and with an instrument of the type indicated above.
An instrument and a system of the type indicated above is shown in DE 25 21 719.
An instrument and a system of the type indicated above are used in open surgery, but preferably in minimally invasive surgery, for cutting tissue in the human or animal body.
In the context of the present disclosure, the instrument indicated above, when used in minimally invasive surgery, can be combined with an endoscope to form what is known as a resectoscope, or it can itself constitute such a resectoscope.
Electrosurgery, or high-frequency surgery, is employed therapeutically in various medical specialties, for example in urology, gynecology, neurosurgery, abdominal surgery, etc. In urology in particular, prostate tissue is removed endoscopically in minimally invasive surgery by means of an instrument of the type indicated above.
In electrosurgical resectoscopy techniques, a distinction is made between monopolar and bipolar application of high-frequency current.
In monopolar application, only the active electrode, sometimes also referred to as the cutting electrode or treatment electrode, is introduced into the treatment region, while the neutral electrode is arranged externally on the patient. Consequently, the current flow between the active electrode and the neutral electrode passes through the patient's body, the disadvantage being that the current path through the patient cannot be safely controlled, the result of which is the possibility of damage to the organs. In addition, the neutral electrode placed on the patient's body may cause burning of the patient's skin.
In the bipolar technique, to which the present disclosure relates, the active electrode and the neutral electrode are both introduced into the treatment region. The current flow can in this way be limited in a controllable manner to the area between the active electrode and the neutral electrode, such that it flows spatially only between the active electrode and the neutral electrode. Accordingly, medical instruments of the type indicated at the outset have been created in which the active electrode and the neutral electrode are arranged on an electrode carrier, in such a way that the active electrode and the neutral electrode can be introduced adjacent to each other into the treatment region.
In bipolar medical instruments of the type indicated at the outset, the active electrode is usually configured with a small active surface area so that a high current density is created on the active electrode, whereas the neutral electrode is usually configured with a relatively large surface area so that only moderate or low current densities are created on the neutral electrode. The active electrode is accordingly used for cutting, while the neutral electrode is intended as far as possible to have no effect on the tissue and is intended simply to limit the current path to the area between the active electrode and the neutral electrode.
In the instrument known from the abovementioned document DE 25 21 719, the neutral electrode is configured as a broad tape, while the active electrode is configured as a wire loop. In a further illustrative embodiment in DE 25 21 719, the neutral electrode, on its side facing away from the active electrode, is covered by a plastic extension, which is connected fixedly to the shaft of the resectoscope.
WO 99/16371 A1 likewise discloses a bipolar medical instrument of the type indicated at the outset. Similarly to the known instrument described above, the active electrode is positioned with respect to the neutral electrode, in the direction transverse to the longitudinal axis, such that they are not spaced apart from each other.
EP 1 163 886 A2 discloses a resectoscope instrument in which the active electrode and the neutral electrode are electrically separated on their mutually facing sides by an insulating body, such that each straight line of connection between the electrodes passes through the insulating body. This is intended to ensure that the direct current flow between the two electrodes is made difficult or is reduced.
The known instruments are either unsuitable for use in particularly small cavities, are too expensive to produce or do not offer sufficient protection for avoiding undesired perforation in the walls of the cavities.